V2
- update build process to
- succeed without bpf_compiler when --enable-bpf-compiler is not set
- succeed with bpf_compiler when this flag is set and libpcap is found
- fail when this flag is set but libpcap is absent
- release memory allocated by pcap on exit
A BPF compiler to convert tcpudmp expressions to the decimal format accepted
by the libxt_bpf.
Generate a file and pass that to iptables:
bpf_compile RAW 'udp dst port 9000' > test.bpf
iptables -A OUTPUT -m bpf --bytecode-file test.bpf -j LOG
Or pass the output directly to iptables using backticks:
iptables -A INPUT -m bpf --bytecode \
"`./bpf_compile RAW 'udp dst port 9000' | tr '\n' ','`" -j LOG
This utility depends on libpcap. The library is only compiled if the option
--enable-pcap is explicitly passed to ./configure and libpcap is found.
Tested (for review: to be removed before merging):
- compilation always succeeds.
- utils/bpf_compile is only built when enable_pcap is true and libpcap is found
- utils/nfnl_osf is (still) only built when nfnetlink library is found
- execution
- tested the above two expressions and verified dmesg output
- logging
- iptables -L INPUT
"
LOG all -- anywhere anywhere match bpf 48 0 0
0,84 0 0 240,21 0 4 96,48 0 0 6,21 0 13 17,40 0 0 42,21 10 11 9000,48 0 0 0,84
0 0 240,21 0 8 64,48 0 0 9,21 0 6 17,40 0 0 6,69 4 0 8191,177 0 0 0,72 0 0
2,21 0 1 9000,6 0 0 65535,6 0 0 0, LOG level warning
"
- iptables-save
"
-A INPUT -m bpf --bytecode "19,48 0 0 0,84 0 0 240,21 0 4 96,48 0 0 6,21 0
13 17,40 0 0 42,21 10 11 9000,48 0 0 0,84 0 0 240,21 0 8 64,48 0 0 9,21 0
6 17,40 0 0 6,69 4 0 8191,177 0 0 0,72 0 0 2,21 0 1 9000,6 0 0 65535,6
0 0 0," -j LOG
"
Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
---
Makefile.am | 2 --
configure.ac | 4 ++++
utils/Makefile.am | 14 ++++++++++++--
utils/bpf_compile.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 72 insertions(+), 4 deletions(-)
create mode 100644 utils/bpf_compile.c
diff --git a/Makefile.am b/Makefile.am
index 6400ba4..c38d360 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -10,9 +10,7 @@ endif
if ENABLE_LIBIPQ
SUBDIRS += libipq
endif
-if HAVE_LIBNFNETLINK
SUBDIRS += utils
-endif
# Depends on libxtables:
SUBDIRS += extensions
# Depends on extensions/libext.a:
diff --git a/configure.ac b/configure.ac
index 27e0b10..e5cfb12 100644
--- a/configure.ac
+++ b/configure.ac
@@ -50,6 +50,9 @@ AC_ARG_ENABLE([devel],
[enable_devel="$enableval"], [enable_devel="yes"])
AC_ARG_ENABLE([libipq],
AS_HELP_STRING([--enable-libipq], [Build and install libipq]))
+AC_ARG_ENABLE([bpf-compiler],
+ AS_HELP_STRING([--enable-bpf-compiler], [Build bpf compiler]),
+ [enable_bpfc="yes"])
AC_ARG_WITH([pkgconfigdir], AS_HELP_STRING([--with-pkgconfigdir=PATH],
[Path to the pkgconfig directory [[LIBDIR/pkgconfig]]]),
[pkgconfigdir="$withval"], [pkgconfigdir='${libdir}/pkgconfig'])
@@ -88,6 +91,7 @@ AM_CONDITIONAL([ENABLE_IPV6], [test "$enable_ipv6" = "yes"])
AM_CONDITIONAL([ENABLE_LARGEFILE], [test "$enable_largefile" = "yes"])
AM_CONDITIONAL([ENABLE_DEVEL], [test "$enable_devel" = "yes"])
AM_CONDITIONAL([ENABLE_LIBIPQ], [test "$enable_libipq" = "yes"])
+AM_CONDITIONAL([ENABLE_BPFC], [test "$enable_bpfc" = "yes"])
PKG_CHECK_MODULES([libnfnetlink], [libnfnetlink >= 1.0],
[nfnetlink=1], [nfnetlink=0])
diff --git a/utils/Makefile.am b/utils/Makefile.am
index f1bbfc5..8b510d6 100644
--- a/utils/Makefile.am
+++ b/utils/Makefile.am
@@ -4,7 +4,17 @@ AM_CFLAGS = ${regular_CFLAGS}
AM_CPPFLAGS = ${regular_CPPFLAGS} -I${top_builddir}/include \
-I${top_srcdir}/include ${libnfnetlink_CFLAGS}
-sbin_PROGRAMS = nfnl_osf
-pkgdata_DATA = pf.os
+sbin_PROGRAMS =
+pkgdata_DATA =
+
+if HAVE_LIBNFNETLINK
+sbin_PROGRAMS += nfnl_osf
+pkgdata_DATA += pf.os
nfnl_osf_LDADD = -lnfnetlink
+endif
+
+if ENABLE_BPFC
+sbin_PROGRAMS += bpf_compile
+bpf_compile_LDADD = -lpcap
+endif
diff --git a/utils/bpf_compile.c b/utils/bpf_compile.c
new file mode 100644
index 0000000..81b59a4
--- /dev/null
+++ b/utils/bpf_compile.c
@@ -0,0 +1,56 @@
+/*
+ * BPF program compilation tool
+ *
+ * Generates decimal output, similar to `tcpdump -ddd ...`.
+ * Unlike tcpdump, will generate for any given link layer type.
+ *
+ * There is no makefile:
+ * compile with `gcc -Wall -o bpf2decimal bpf2decimal.c -lpcap` or similar.
+ *
+ * Written by Willem de Bruijn (willemb@xxxxxxxxxx)
+ * Copyright Google, Inc. 2013
+ * Licensed under the GNU General Public License version 2 (GPLv2)
+*/
+
+#include <pcap.h>
+#include <stdio.h>
+
+int main(int argc, char **argv)
+{
+ struct bpf_program program;
+ struct bpf_insn *ins;
+ int i, dlt = DLT_RAW;
+
+ if (argc < 2 || argc > 3) {
+ fprintf(stderr, "Usage: %s [link] '<program>'\n\n"
+ " link is a pcap linklayer type:\n"
+ " one of EN10MB, RAW, SLIP, ...\n\n"
+ "Examples: %s RAW 'tcp and greater 100'\n"
+ " %s EN10MB 'ip proto 47'\n'",
+ argv[0], argv[0], argv[0]);
+ return 1;
+ }
+
+ if (argc == 3) {
+ dlt = pcap_datalink_name_to_val(argv[1]);
+ if (dlt == -1) {
+ fprintf(stderr, "Unknown datalinktype: %s\n", argv[1]);
+ return 1;
+ }
+ }
+
+ if (pcap_compile_nopcap(65535, dlt, &program, argv[argc - 1], 1,
+ PCAP_NETMASK_UNKNOWN)) {
+ fprintf(stderr, "Compilation error\n");
+ return 1;
+ }
+
+ printf("%d\n", program.bf_len);
+ ins = program.bf_insns;
+ for (i = 0; i < program.bf_len; ++ins, ++i)
+ printf("%u %u %u %u\n", ins->code, ins->jt, ins->jf, ins->k);
+
+ pcap_freecode(&program);
+ return 0;
+}
+
--
1.8.1.3
--
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